It is often desirable to modify the surface interface of polymeric materials to produce a variety of related surface effects such reduced surface energy, improved slip, reduced coefficient of friction, improved lubricity, reduced blocking, and to lubricate process equipment. It is also desirable to modify polymeric surfaces to improve release of adhesives and promote demolding or abhesion of other materials from metal and other polymeric composition surfaces.
Many patents utilize exotic and commercially un-desirable species of polysiloxanes as additives for thermoplastics. For example, U.S. Pat. No. 4,499,149 discloses polydiorgani-siloxanes that have very polar end groups, and aromatic termination in the alpha and omega positions. This patent discloses diorgano siloxane functionalities with shorter chain di-alkyl groups having from 1 to 12 carbon atoms in length. The main focus of the '149 patent is on the end group chemistries of these compounds in order to gain compatibility of the siloxanes with polar polymers.
U.S. Pat. No. 5,567,531 also utilizes difficult to produce exotic chemistries in the terminal linkages of a polysiloxane compound to obtain improved compatibility of the compound with polymeric compositions. In particular, the pendant alkl groups on the back bone of the siloxane compound are also limited to propyl or fluorinated species. However, as a result of this structure, the siloxane materials disclosed in the '531 patent are not able to form convenient melt processable waxes with the polymeric compositions to which they are added.
U.S. Pat. No. 6,472,077 utilizes the Dow Corning MB50 additive to produce a block resistant film. This chemistry of the film is based primarily on high molecular weight dimethylpolysiloxane. However, these siloxane materials require careful and proprietary masterbatch processing technology to produce the MB50 additive. In addition many applications of this additive are sensitive to the transfer and migration ability of the MB50 additive through the polymeric composition within which the MB50 additive is incorporated, which is often highly undesirable.
U.S. Pat. No. 4,692,379 discloses the use of a polydimethylsiloxane oil to modify the coefficient of friction of polymeric films. This type of siloxane oil has been demonstrated many times to be an excellent lubricant, but suffers from severe incompatibility in many polymeric systems, and its resultant rapid migration out of the polymeric compositions within which it is utilized causes a variety of downstream processing and handling problems with the polymeric compositions including it. In addition, liquid silicone oils are very difficult to process in melt extruders.
U.S. Pat. No. 7,105,233 describes in detail the benefits and use of higher molecular weigh alkyl functional diorganofunctional siloxanes in polyolefins. However, the disclosed method of producing the long chain alkyl functionality utilizes the reaction of a long chain alcohol with hydrosiloxanes to produce a number of alkoxy bonds (Si—O—R) in the molecule. It is very well established in the art that alkoxy bonds are reactive and reversible. In particular, they are reactive in the presence of any moisture and hydrolytically cleave to produce a silanol and an alcohol leaving group. This chemistry is described in detail in the “Chemistry and Technology of Silicones” by Walter Noll. Numerous other papers are available considering the various kinetics and reversibility of this bond. In addition, the presence of acidic or basic conditions, as well as heat, can be catalytic and greatly accelerate this degradation process. Many times potentially catalytic species are used as fillers or pigments in the compounding of polymeric materials. Moisture is almost always present, often carried in by other additives combined in the polymeric composition. When the compounds including the types of additives discussed in the '233 patent are melt processed under high heat, they create the conditions conducive to the degradation of the alkoxy functional additive. Use conditions for the polymeric compositions including these additives are also often harsh and with time can also drive the degradation of the additive containing the alkoxy linkage. The resultant silicone and long chain alcohol degradation products do not provide the same surface modification benefits that the original alkyl alkoxy modified siloxane. In fact, these decomposition products are very migratory, transient and can cause process problems down stream.
Therefore, it is desirable to develop a siloxane additive for use in various polymeric compositions that provides the desired benefits to the compositions described above, but without the potential or the problems associated with the migration, degradation, and compatibility issues associated with prior art siloxane additives compounds.